Projecting apparatus



1 Sept. 29, 1942. 'A. BRlECl- ILE ETAL PROJECI'ING APPARATUS Original Filed Sept. 9, 1938 4 Sheets-Sheet'l INVENTORS.

ATTORNEY.

pt- 9,1942: v A. macaw AL I 2,296,928

PROJECTING APPARATUS Y ATTORNEY.

Sept. 29, 1942.

BRIECHL E- ET AL PROJECTING APPARATUS 4 Shets-Sheet 3 Original Filed Sept. 9, 1958 ATTORNEY.

.Sept. 29, 1942. A. BRIECHLE ETAL PROJECTING APPARATUS Original Filed Sept. 9, 1938 4 Sheets-Sheet 4 Patented Sept. 29, 1942 UNITED STATES PATENT OFFICE PROJECTING APPARATUS ware Original application September 9, 1938, Serial No. 229,096. Divided and this application February 26, 1940, Serial No. 320,758

13 Claims.

This invention relates to apparatus for producing a photographic image and for locating a point on said image.

This application is a division of copending application Serial No. 229,096, for Apparatus for and method of producing and utilizing a photographic image, filed September 9, 1938.

An object of the present invention is to provide novel apparatus for accurately rectifying and projecting the image of an aerial photograph on a screen;

Another object is to provide the apparatus embodying the above with a novelly located secondary projecting system for producing a conveniently disposed and easily read record of data relating to the main or primary projection.

Still another object is to provide novel means for locating a point on the primary projection.

A further object is to provide novel means for readily and rapidly loading film into position for projection.

Still another object of the invention is to provide novel means for fixing the film in a plane during projection and for accurately centering said film.

A still further object is to provide a novel apparatus embodying the above features which is compactly constructed and which provides a large, clear image of uniform intensity.-

The above and further objects and novel features of the invention will more fully appear from the following detailed description when the same is taken in connection with the accompanying drawings. It is to be expressly understood, however, that the drawings are for the purpose of illustration only and are not designed as a definition of the limits of the invention, reference being had for this latter purpose to the appended claims.

In the drawings, wherein like reference characters refer to like parts throughout the several views,

Fig. 1 is a front elevation of one embodiment of the apparatus for carrying out the present invention;

Fig. 2 is a sectional view taken substantially along line 2-2 of Fig. 1;

Fig. 3 is a somewhat enlarged sectional view taken along line H of Fig. 2 showing in detail a source of illumination and film carrying mechanism;

Fig. 4 is a sectional view taken substantially along line 44 of Fig. 3 showing a formvof film metering and film loading mechanism;

Fig. 5 is a rear elevation partly in section,

section being taken along line 5-5 of Fig. 4, and includes the details of a novel reversing film drive and the pivotal mounting of the film holding and illuminating member;

Fig. 6 is an enlarged sectional view of the secondary projecting system shown in Fig. 2 illustrating in detail a film holding carriage and means for mounting the same in operative position;

Fig. 7 is a sectional view taken substantially along line 1-7 of Fig. 6;

Fig. 8 is a top plan view of the film holding carriage removed from operative position in the projector;

Fig. 9 is a sectional view taken substantially along line 9-9 of Fig. 2 showing in detail the mechanism for locating a point on a projected image in accordance with known data;

Fig. 10 is an enlarged section taken substantially along line l0|0 of Fig. 9; and,

Fig. 11 is a top plan view of a device for eliminating parallax in the point locating mechanism.

In the single embodiment illustrated, by way of example, the present invention comprises a main projecting system (Fig. 2) which includes a source of illumination II, a film l2 fixed between a pair of glass plates l3 and H, a lens l5 and a ground glass or other suitable translucent screen l6, upon which the image of the filmis projected and viewed. Glass plate I against the face of which film I2 is resiliently urged by means to be hereinafter described, is suitably fixed to a casing I! having an inwardly projecting conical portion I8 at the apex of which lens I5 is suitably secured. Screen I6 is secured to casing i! at the front end thereof by suitable means, such as clamps l9. Thus, an image of photograph or film l2 will be projected upon ground glass l6 whenever the source of illumination ll is energized. Furthermore, film l2, which is taken by a bombing camera when the latter is inclined at a predetermined angle to the surface of the earth, is fixed in the projecting system by plate H in a manner to produce a rectified image on screen l6 when projected.

The source of illumination ll, shown as comprising a group of incandescent lamps 20 (Figs. 2 and 3) is preferably enclosed in a separate housing 2i provided with sockets 22 in which said lamps are mounted. In order to produce a projected image of uniform intensity on ground glass I6, said lamps are of varying sizes, the

' intensities of illumination thereof being directly dependent upon the degree of enlargement proth 5 duced thereby. A heat absorbing glass plate 23 is mounted in housing 2|, being interposed between lamps and film l4 for the purpose of protecting the film from he heat given off by the lamps. A second glass plate 24, preferably of the ,same composition and provided for the same purpose, is mounted on the outside of casing 2| by means of brackets 25. A frame 26 in which the glass covered end of housing 2| telescopes is slidably mounted on said housing by means of pins 21 (Figs. 3 and 4) each of which has one end rigidly fixed to frame 26 and the other end extending into said housing. The extending end in each instance has a collar 29 fixed thereon for the purpose of limiting the movement of said plate relative to said housing. Coil springs 29 are interposed between the latter, surrounding pins 21 and urging said plate away from said casing. An opening 30 centrally located in said cover plate is covered by glass plate l3, the latter being secured to said cover plate by suitable means, such as screws 3|. Film I2 located between plates I3 and i4 is normally urged into the plane of the face of the latter plate by the pressure of the former.

In order to relieve the film l2 of the force exerted thereon by plate I3 and thereby allow movement of said film, novel means are provided for displacing plate l3 against the expansive pressure of springs 29, said means comprising cam members 32 (Fig. 4) which are adapted to bear against the frame 26 in which plate I3 is mounted and which are fixed to shafts 33, for rotation therewith. The latter are journalled in brackets 34 (Fig. 3) integral with or secured to casing l1 and each has an arm 35 rigidly fixed thereto. The free ends of said arms are joined by a link 36, (Fig. 4) and the latter is in turn connected by means of arm 31 to a shaft 39. When shaft 38 is moved longitudinally to the left as viewed in Fig. 4, arm 31 is moved upward causing link 36 to move likewise and rotate arms 38 in a counter-clockwise direction. Rotation of said arms causes a similar rotation of cam members 32 and thereby displaces frame 26 in the direction of housing 2|.

When the pressure upon film I2 is removed, the same becomes free to move and novel means are provided for mounting and moving said film. Film rolls 39 (Figs. 3 and 4) are provided on opposite sides of housing 2| and film I2 is adapted to unwind from one and be wound upon the other, being guided during movement by means of idler rolls 40 suitably journalled on opposite sides of frame 26 in brackets 4| fixed to said frame. Both of said film rolls are similarly mounted between flanges or brackets 42, which extend outwardly from housing 2 I, being rigidly secured thereto or formed integrally therewith. Upper flanges 42 have centrally located trunnions 43 (Fig. 4) which engage openings 44 in the upper ends of film rolls 39, thereby creating a pivotal support for said ends permitting relative rotation of said film rolls about said trunnions. Lower flanges 45 are provided with trunnions 46 which engage openings 41 in the lower ends of film rolls 39 in a driving connection, said trunnions having upwardly extending prongs 48 which fit into radial slots 49 in said film roll ends. Trunnions 46 are slidably mounted in openings 50 in said lower flanges and when moved downwardly, disengage from film rolls 39. Each of the latter trunnions has a shaft 5i fixed thereto and said shaft extends through the flange and has a helical gear 52 fixed to the end thereof, said gear bein adapted to bear against a lug or stop 53 formed with casing l1 and thereby maintain trunnion 46 and prongs 48 in engagement with opening 41 and slots 49.

Novel means are provided for moving film l2 during operation of the projector and comprise a helical gear 54 (Fig. 5) which drivably engages gear 52 and which is mounted on a shaft 55 journalled for rotation in a bracket 56, the latter being formed integrally with casing l1. A toothed clutch member 51 is fixed to shaft 55 and a cooperating clutch member 59 is slidably mounted on said shaft, having a helical gear 59 integral therewith. The latter gear meshes with a gear 60 fixed to shaft 6| (Figs. 2 and 5) which is journalled in a bearing 62 provided therefor in casing 11, said shaft having an end thereof extending into said casing and a jaw clutch element 63 mounted on said end. It is well-known that when one helical gear drives another, a thrust is applied to that other gear along its axis of rotation in a direction depending on the direction of rotation of the first. Therefore, since gear 59 is slidably mounted on shaft 55, rotation of helical gear 66 in a clockwise direction as viewed in Fig. 5 causes gear 59, together with clutch member 59 to move to the left and causes the latter to drivably engage clutch member 51, thereby completing a drive from jaw clutch member 63 to the left film roll 39 of Fig. 3.

In order to make it possible to drive the film in either direction. a similar clutch mechanism comprising members 64 and 64a is provided on the right side of helical gear 59, a shaft 65 being secured to clutch member 64a, shaft 65 is, in turn, connected to the right hand film roll (Fig. 3) by the driving connection hereinbefore described which includes helical gear 52 and trunnion 46. Therefore, when gear 69 is rotated in a counterclockwise direction, shaft 65 is drivably connected by means of clutch members 64, 64a to the right-hand film roll (Fig. 3).

Jaw clutch member 63 from which the film rolls are driven is adapted-to engage a clutch member 66 when the latter is moved axially with shaft 38. The latter is suitably journalled in a bracket 61 fixed to casing l1 and a bearing 69 (Fig. 2) integral with said casing and extends beyond the front face of said casing. A readily accessible hand crank 68a is mounted on the extending portion of said shaft and when the latter is moved longitudinally by means of said crank, it causes the jaw clutch to drivably engage so that rotation of said crank will thereafter move film I2. In order to drivably engage the clutch 63, 66 and move film l2, shaft 38 must be moved longitudinally (to the left as seen in Fig. 4) and, as hereinbefore pointed out, this' movement causes frame 26 to be displaced relieving film l2 of any frictional forces which might tend to oppose the motion of said film.

As a means for facilitating film loading, housing 2| is pivotally mounted for rotation relative to casing l1 and is adapted to be pivoted, together with film rolls 39 and frame 26, away from said casing during the loading operation. For this purpose, housing 2| is equipped with a pair of downwardly extending hinges or brackets 69 which are mounted on shafts 55 and 65, one of said hinges being shown in Fig. 5. When said housing is moved away from casing l1, film rolls 39 are moved therewith, but helical gears 52 (Fig. 4) tend to remain fixed and therefore said film rolls move upward relative to trunnions 46 to become disengaged from the latter. Thereafter. said film rolls are held in place by rods 10 which are fixed in flanges 42 and 45 and'extend therebetween. As shown, three of said rods are provided for each film roll and effect a three-point support for that roll which approximately centers the same. Thus, film rolls 39 are free to be removed and replaced after housing 2| is pivoted away from casing I1 and the film can be threaded readily from one film roll to the other over idler rolls 40. Furthermore, when housing 2| is again pivoted into operative position, the newly positioned film rolls are automatically reengaged by trunnions 48.

Housing 2| is held in operative position by a latch member II (Fig. 4) one end of which engages and grasps a lug I2 cast integrally with said housing. The other end of said latch member is pivotally mounted by means of a pin I3 to a bracket I4 secured to casing II.

In addition to the primary or main projecting system heretofore described, a secondary system for projecting a record of instrument readings made concurrently with the taking of the main film is provided. The latter is shown (Figs; 2 and 6) as utilizing source I I for illumination and as projecting the recorded readings on screen I6 beneath the main projection. A chamber I5 for housing the secondary film carrying mechanisms is preferably formed in the base of casing I'I, said chamber having openings I6 and II in opposite end walls thereof so that the light given off by lamps 20 may pass through said chamber to screen I8. At least one side of chamber I5 is open to admit a carriage 18 on which the film carrying mechanism is mounted, said carriage being slidably insertable into said chamber on a pair of guides or tracks I9 fixed to the fisor of said chamber by screws 89. Carriage I 8 is provided with a pair of downwardly extending flanges 8| to which a pair of runners 82 are secured, the latter being adapted to cooperate with guides I9 to form a means for readily inserting and positioning said carriage in chamber I5. brackets 84 extending from carriage I8 and fa cilitates the insertion and removal of said cariiage into and from chamber I5.

A mask 85 for fixing the plane of secondary film 85 (Fig. 6) during projection is formed by a vertical wall 81 integral with carriage I8 and a hinged member 88 pivotally mounted to the base of said carriage by means such as pins 89 extending through said base and said member. The latter, pivots into close engagement with wall 81 and a slot 90 is formed between the two when so engaged, by which film is guided during movement and fixed during project-ion. Openings 9| are provided in said wall and in said mem er and register when the two are brought into engagement in order to permit the projection therethrough of the data recorded on the film, said openings are, however, not as wide as slot 90 and. therefore, the edges of the film remain within and guided by said slot. A latch, shown as comprising a resilient element 92 provided with an overlapping portion 92a, is secured to a bracket 93 integral with wall 81 and is adapted to engage and hold hinged member 88 when the latter is moved into contact with said wall.

Secondary film 88 is carried by a pair of film rolls 94 mounted for rotation on carriage I8 and is unwound from one roll, passing over an idler 95 (Fig. 8) through mask 85 and then over a second idler 95 to the second of said rolls being wound thereon. Both film rolls are mount A handle 83 is fixed between a pair of ed on and rotatable with vertical shafts 96 which extend through the base of carriage I8 and which are journalled in bearings 91 provided in said base (Fig. 7). Gears and 89 are fixed to said shafts beneath said base at different distances from said base, gear 98 which enters chamber I5 foremost as carriage I8 is inserted being mounted more closely to the base than gear 99. Accordingly, when carriage 18 is inserted into said chamber, gear 98 clears a gear I00 secured to a shaft IOI journalled in the fioor of said chamber and engages a gear I02 secured to a shaft I03 journalled in the floor of said chamber further along the path of motion of said carriage. Gear I00 which is mounted on a lower plane than gear I02 engages gear 99 and thus both film roll gears become drivably engaged when carriage I8 is operatively positioned. Shafts IOI and I03 extend beneath the fioor of chamber I5 and have bevel gears I04 and I05, respectively, secured thereon. Each of said bevel gears is adapted. to be driven from one of a pair of bevel gears I06 meshing therewith. The latter gears are mounted on coaxial shafts IOI driven from a helical gear drive similar'to the drive hereinbefore described as actuating film rolls 39 on which the main film is wound. The drive comprises a pair of toothed clutches I08 and I09 operatively mounted on each side of a helical gear III) which meshes with a second helical gear III, the engagement of said clutches depending on the thrust imparted by gear III. The latter gear is secured to a shaft II2 journalled in brackets Ii3 which are fixed to the floor of chamber I5, said shaft being directly connected to a flexible shaft II4 which is, in turn, operatively connected to a hand crank I I5 (Fig. 1). When said hand crank is rotated the secondary film rolls 94 rotate in a direction determined by the direction of rotation of said hand crank and the latter is thereby adapted to move film 88 in either direction during projection.

A bracket IIG secured to the fioor of chamber I5 by suitable means, such as screws III, has

' a lens IIB mounted therein, said lens being correctly positioned to focus the image of the seccndary film on screen IS.

A novel mechanism is provided in the present invention for the purpose of locating a point, such as the theoretical point of impact of a bomb, on the image of the main projected photograph in accordance with the recorded date of the secondary projection. A hollow ring 9 (Fig. 2) is pivotally mounted on the face of casing I1, preferably by means of ball bearings I20 which are fixed to said casing and are engaged by a track or groove I 2| provided on the interior of outer wall I22 of said ring. The latter may be rotated relative to casing I! and a scale ll9a preferably calibrated in degrees is provided beneath said ring on casing II to indicate the angular displacement of said ring.

Four like pulley systems I23, I24, I25 and I26 (Fig. 9) are secured to inner'wall I21 of ring II9, being completely enclosed by and movable with said ring. Opposing systems, namely, systems I24 and I26, and systems I23 and I25, are disposed parallel to each other and each of said systems comprises a bracket I20 which is shown fixed to inner wall I21 and which preferably has a bifurcated member I29 integral therewith. A rod I30 is threadedly secured at one end to said bracket and has a bifurcated member I3l similarly secured at the other end. A bracket I32 rod I by having an opening therein through' which said rod extends. A pulley I33 is mounted for rotation on a shaft I34 fixed between the arms of bifurcated member I29 and a second pulley I35 is similarly mounted on a shaft I36 extending between the arms of. member |3|. A belt I31, preferably composed of a spring steel, is passed over said pulleys, the ends of said belt being joined together by a coupling member I38 bolted or pinned thereto. The tension in belt I31 is maintained or varied by rotation of rod I30, the latter being provided with a right-handed thread at one end thereof, and a left-handed thread at the other end, and having bolts I39 mounted thereon for locking the same after adjustment.

Coupling members I36 of belt systems I23 and I25 also serve to securely fix the ends of a crosshair I40 to the belts I31 of said systems, so that said crosshair is stretched tightly across the face of ground glass I6 in proximity to the surface thereof. A second crosshair MI is similarly mounted across the belts of systems I24 and I26 to intersect crosshair I40 at right angles, each of said crosshairs being adapted to have a parallel motion and always intersect the other at right angles, determining a point on the image by the intersection. In order to insure that a parallel motion of crosshair I40 be maintained, a flexible shaft I42 is provided for connecting the shafts I34 on which pulleys I33 of systems I23 and I25 are mounted, synchronizing the rotary motion of said pulleys. Similarly, a flexible shaft I43 connects pulleys I33 of systems I24 and I26, and controls the motion of crosshair |4I.

Each of flexible shafts I42 and I43 is adapted to be actuated from the exterior of ring II 9 so that the motion of the respective crosshairs may be governed from the frontof the projector. For this purpose, each of said flexible shafts is provided with a worm wheel I44 which is drivingly engaged by a worm I45, the latter being mounted on a shaft I46 (Fig. 10) which extends through the central wall of ring 9. A disc I41, having a knob 48 fixed thereto, is secured to the end of shaft I46 and is readily accessible from the front of the projector for moving the crosshair to which it is connected.

In order to be able to displace the crosshairs a known distance and locate a point on the image in accordance with known data, a pair of callbrated dials I49 and I50 (Fig. 10) is provided for cooperating with each crosshair actuating mechanism. Each pair of dials accurately indicates the angular displacement of disc I41. said angular displacement being a measure of the movement of the crosshair controlled by said disc. Dials I49 and I50 are directly connected to each other by a gear reduction drive comprising a gear |5I integral with a collar I52 on which dial I49 is mounted and which is freely journalled on shaft I46. Gear |5| meshes with a gear I53 pivotally mounted on a shaft I54 pinned to the central wall of ring I I9 and drives a smaller gear I55 mounted concentrically with gear I53. Gear I55 in turn engages a gear I56 formed with dial I50 and thereby completes a drive to said dial from dial I49. Accordingly, dial I50 by a suitable choice of gearing may be adapted to give a reading of the number of revolutions rotated by disc I41, while dial I49 gives a reading of the portion of a revolution moved by said disc. The former dial is located within ring H9 and is visible through an opening I51 provided In the face of said ring, whereas the latter dial is mounted on said face concentric with and beneath disc I41. The edge of dial I49 extends beyond the edge of disc I41 and the readings thereon may be viewed from the front of the projector.

Normally, dial I49 is connected to disc I41 and is constrained to move together therewith, recording the amount of movement imparted to the crosshair by said disc. The connecting means between said dial and said disc comprises a pin I59 slidably mounted in a recess I59 provided therefor in disc I41, and normally urged in the direction of dial I49 by a spring I60 interposed between said disc and a shoulder on said pin. A metal plate |6|, having a knurled or toothed edge, is mounted on the face of dial I49 and when the base of pin I58, which is also knurled, is held in engagement therewith by spring I60, a driving connection between said dial and disc I41 is effected. Whenever the displace ment of each crosshair from a reference point is to be measuredfit is desirable that the dials be set at zero when the crosshairs are moved to that reference point. Accordingly, a knob I62 is fixed to the end of pin I58 which extends beyond the outer surface of disc I41, making it possible to manually raise said pin out of contact with plate |6| and disengage the crosshair actuating mechanism from the indicating mechanism so that each might be set independently of the other.

For extremely accurate work, a frame I63 (Fig. 11) may be slidably mounted on crosshairs I40, I and actuated thereby. A glass plate I64 is mounted in said frame and has reference lines I66, I66 engraved thereon, the intersection of said lines being used instead of the intersection of the crosshairs to locate a point on the image. By locating the reference lines in the same plane, all parallax is eliminated and the accuracy with which a point may be determined is accordingly increased.

In operation, a roll of film taken during the simulation or an actual bombing flight is removed from the camera, suitably developed and rewound upon a film roll 39, and thereafter loaded into the novel apparatus of the present invention for projection. The film loading operation consists in disengaging latch number 1| from lug 12 (Fig. 2) and causing housing 2| to swing on hinges 69 away from casing I1. With the housing thus displaced, film roll 39 is dropped into one of the two three-point supports constituted by rods 10, and the film I2 is then partially unwound from said film roll and threaded over idler rolls 40 and glass plate I3 and secured to a second film roll 39, which is positioned in the second of the three-point supports formed by rods 10. Housing 2| is now swung back into operative position and latch member 1| is pressed into engagement with lug 12 to lock said housing to casing I1 and to fix a frame of film I2 between plates I3 and I4. Said film frame may thereafter be projected on screen I6 by energizing light bulbs 20 mounted in said housing;

In the interval during which housing 2| is pivoted in a clockwise direction (Fig. 4) to operative position, the film rolls 39 become drivingly engaged by trunnions 93 and 96. Lug 53 limits the motion of shaft 5| and thereby causes movement of film rolls 39 relative to trunnions 46. The latter movement in turn causes openings 41 in said film rolls to be engaged by trunnions 40 and openings 44 to be engaged by trunnions 43.

Accordingly, when it becomes desirable to move film I2 to project a new frame thereof, crank 64a is first moved longitudinally (to the left as viewed in Fig. 2) until clutch member 88 engages member 83, and plates I3 and I4 are separated .to free film I2 for movement. Rotation of crank 88 is thereafter transmitted through helical gear 88 to gear 88 and tends to move the latter gear axially to cause one of clutches 51, 58 and 84, 84a to become engaged thereby completing a drive to oneof film rolls 38. Further rotation of crank 88a rotates the film roll and moves film I2 through the drive which includes the one of clutches 51, 58 and 84, 84a which is engaged, shaft 85 or 85, depending on which of said clutches is engaged, gear 54, gear 52, and trunnion 48 (Figs. 4 and 5). The above drive from crank 88a permits any desired exposure on film I2 to be located between plates I3 and I4 for projection on screen I8.

With the main or primary film I2 mounted and positioned for ready movement, the next step in the determination of the theoretical point of impact of a bomb on the projection of the first of each series of photographs is to make available to the operator of the projecting apparatus certain flight data recorded (either photographically or by hand) at the time said photograph is taken. If photographically recorded, the film carrying the record is wound on film roll 84 and the cutter is mounted on one of shafts 88 of carriage 18 (Figs. 6 and 8). The film 88 is threaded over idler rolls 85 and the face of vertical wall 81 to second film roll 84, hinged member 88 being pivoted away from said wall to facilitate said threading. With film 88 thus threaded member 88 is moved into contact with wall 81 and is engaged by latch 8i to form mask 85 and to fix the film in slot 88 of said mask.

Carriage I8 is then slidably inserted into chamber I5 of easing I1, said insertion causing film rolls 84 to become drivingly connected to gears I88 and I82 (Fig. 'I) by means of gears 98 and 88, respectively. The frame of film 88 fixed in mask 85 may now be projected on screen I8 by energizing light bulbs 28, the path of light being through openings I8 and SI, lens system H8 and opening TI to said screen.

When main film I2 is positioned to cause the projection of a new frame thereof, secondary film 88 is correspondingly positioned to project the record of the conditions under which said film frame was taken. The movement of film 88 is effected by rotation of crank II5 which rotates helical gear I I I by means of the flexible cable I I4 and actuates the drive to either gear I88 or gear I82, said drive comprising helical gears III and H8, clutches I88 and I88, shafts I81 and gears I88, I85 and I84 (Fig. 6).

To determine the point of impact of a theoretical bomb, crosshair I48 is located parallel to a line on the projected image which corresponds to the line of flight of the plane with respect to the ground. Since the photograph is taken with the center line thereof parallel to the longitudinal axis of the plane, the desired parallelism may be produced by rotating ring H8 through an angle equal to the angle at which the plane was crabbed when the photograph was taken. This angle of crab is determined from the first and second photographs of a series in a manner to be hereinafter described and may be measured on scale lI8a.

The crosshairs ar'e thereafter moved to a datum point and the two sets of indicating dials I58 and I48 are preferably adjusted to read zero.

The datum point over which the intersection of crosshairs I48, I is fixed is the point on the projected image which was directly beneath the plane at the moment the photograph was taken, to be hereinafter referred to as the plumb point. Said plumb point is readily located on the projected image since it bears a fixed relation to the boundaries of each projected image and may be permanently marked of! on screen I8. When crosshair I48 coincides with, said point, it traces on the projection the line of flight of the plane with respect to the ground and therefore it the actual or imaginary bomb was released at some known interval before or after the photograph was taken, the point of release may be readily determined. The ground speed and the interval as well as the scale of the proiection being known, crosshair I may be moved along crosshair I48, i. e., along the line of flight, a distance determined from the above data to the point above which the bomb was released.

The drift of the actual or imaginary bomb, 1. e., the movement of the bomb at right angles to the path of flight, after release is a function of the altitude and crab angle of the plane, both of which are known so that it is possible to provide a table or alignment chart from which said drift may be picked off. Crosshair I48 is thereafter moved by means of disc I41 from the line of flight a distance which on the projected image is equal to the drift of the bomb, the distance being measured by dials I48 and I58, and said table or chart preferably giving the value of said drift as a reading of said dials.

The forward movement of the bomb in the direction of the line of flight will depend on the speed of the plane, the altitude and the magnitude of the component of wind velocity in that direction. These variables are given or are readily determinable from the recorded flight data and a suitable chart or table gives the readings to which dials I48 and I58 are to be set in order to move crosshair III a distance on the main image equivalent to the forward flight of the actual or imaginary bomb from the point of release thereof. When both crosshairs have been thus moved, the point of intersection designates the point of impact of the bomb.

The crab angle of the plane for each bomb release is preferably determined by projecting the first two photographs of each series on screen I8 and locating on the second photograph the object which was the plumb point of the first. The angle between a line joining said object and the plumb point of the second photograph and a line along the vertical center line of the image is the crab angle.

There is thus provided a novel apparatus which incorporates, among other features, a novel means for locating a point on a projected image, and a novel mechanism whereby corresponding exposures on a plurality of separate films may be projected on a single screen. The projecting mechanism includes novel means for. loading, mounting and metering one or more films. The apparatus embodying the above novel features is compact in form and produces a large, clear image of uniform intensity on which the various reference points may be readily located.

Although only a single embodiment of the invention has been illustrated and described in detail, it is to be expressly understood that the same is not limited thereto but that various changes may be made therein without departing from the spirit and scope of the invention. For a definition of the limits of the invention, reference will be had primarily to the appended claims.

What is claimed is: 1. In a projecting unit, means for producing an image of a photograph, said means comprising a supporting member, a screen carried by said member, lens means fixed by said member relative to said screen, mechanism for fixing film in the focal plane of said lens, and illuminating means, said mechanism and illuminatin means being pivotally mounted relative to said supporting member, and means for metering the film, said last-named means comprising a pair of film roll retaining members carried by said mech. anism, a pair of film rolls carried by said film retaining members and driving means centrally engaging said film rolls in one extreme pivotal position of said mechanism and disengaged from said film rolls in the other extreme pivotal position of said mechanism.

2. In a projecting unit, a casing, a screen carried by said casing, a projection chamber in said casing, means for fixing film in a predetermined relation to one end of said chamber, lens means mounted at the other end of said chamber to project images from said film on said screen, metering means for the fiim, a second projection system in said casing for producing an image on said screen, said system comprising film fixing means, film metering means and lens means, common illuminating means for both of said projection systems, and means operable from the screen end of said casing for actuating each of said metering means.

3. In a projector for producing a rectified image of an aerial photograph and an image of recorded fiight data taken at a predetermined time relative to said photograph, a stationary casing, a screen carried by said casing, a pair of separate projection chambers in said casing. film retaining means contained in each of said chambers, lens means mounted in each of said chambers for projecting images on said screen, a common source of light for said chambers, and means for actuating said film retaining means to obtain related images on said screen.

4. In a projecting apparatus of the class described, a housing unit, screen mean mounted in said housing unit, a film projecting system for producing rectified images on said screen means, said system comprising lens means, means for fixing a frame of film in the focal plane of said lens means, and means for metering the film, a second projecting system comprising lens means, means for fixing film in the focal plane of said lens means, means for metering the film. said second projecting system being contained in a chamber formed in said housing unit and separate from said first projecting system, common illuminating-means for said projecting systems, and means readily accessible from the screen end of said housing unit for actuating the film metering means.

5. In apparatus for producing a rectified image of an aerial photograph and an image of flight data photographically recorded at a predetermined time relative to said photograph, a housing unit, a screen'carried by said unit,-a film projecting system contained in said housing unit, said'system comprising film retaining means, and lens means, a second film projecting system contained in said housing, a pair of chambers in said housing for containing elements of each of said projection systems and for separating the light paths of said systems between the film and lens means thereof, a common illuminating means for said systems, and means for metering the films projected by said systems, said metering means comprising actuating elements operable from the screen end of said housing unit.

6. In a projecting unit, a casing, a screen carried by said casing, a projection chamber in said casing, lens means mounted in said chamber, means including film rolls for mounting a roll of film with a frame thereof in the focal plane of said lens means, a housing for carrying said film mounting means, said housing being pivotally mounted on said casing, illuminating means in said housing, and actuating means operable from the screen end of said casing, said actuating means being connected to the film rolls for meter-.

ing the film and for holding said rolls against removal, pivotal movement of said housing away from said casing being adapted to disconnect said actuating means from said film rolls.

7. In an image projecting device, a casing, a screen mounted in the front end of said casing, a projection chamber in said casing, lens means mounted in said chamber, means including film rolls for mounting a roll of film with a frame thereof in the focal plane of said lens means, a housing supporting said film mounting means on the exterior thereof, said housing being mounted on the rear end of said casing, illuminating means supported in said housing, and actuating means operable from the screen end of said casing, said actuating means being operatively connected to the film rolls for metering the film and for holding the rolls against removal,

8. In a projecting unit, a casing, a screen at the front end of said casing, lens means mounted in said casing, transparent means mounted at the rear end of said casing in the focal plane of said lens means, means including film rolls for mounting a roll of film with a frame thereof in engagement with said transparent means, a housing carrying said film mounting means on the exterior thereof, iluminating means mounted on the interior of said housing, and drive means operable 'from the front end of said casing for metering prising lens means and a transparent plate in the focal plane of said lens means, means for mounting a roll of film, said mounting means including film rolls and a member resiliently urging a frame of the roll of film carried by said film rolls into engagement with said transparent plate, a

housing carrying said film mounting means on the exterior thereof, said housing being mounted on said casing, illuminating means operatively mounted on the interior of said housing, and drive 4 ing and metering means, common illuminating means for said system carried by said housing,

and separate means operable from the screen end of said housing for actuating each' of said film carrying and metering means.

11. In apparatus oftheclassdescribedahousing.

screen means mounted on said housing, a film projecting system for producing images on'said screen means, said system comprising film carrying means, metering means and lens means, a second projecting system separately contained in said housing for projecting images on said screen, said second system comprising film carrying means, metering means and lens means, and means operable from the front end of said housing for actuating each of said film metering means.

12. In a projecting unit, means for producing an image of a photograph, said means comprising a casing, a screen carried by said casing, lens means mounted in said casing, illuminating means, and mechanism for fixing film in the i'ocal plane of said lens means, said'mechanism being pivotally mounted relative to said casing, and means for metering the film, said 12 st-named means comprising a pair of film rolls, retaining members for said film rolls, said fiim rolls and retaining members being carried by said mechanism, and driving means operatively engaging said film rolls in one extreme pivotal position of said mechanism and being disengaged from said film rolls in the other extreme pivotal position of said mechanism.

13. In a projecting unit, m'ans for producing an image of a photograph, said means comprising a supporting member. a screen carried by said member, lens means mounted in said member, illuminating means mounted on said member and mechanism for fixing film in the focal plane of said lens means, said mechanism being pivotally mounted relative to said supporting member, and means for metering the film, said last-named means comprising means for mounting a roll of film and drive means engaging said film mounting means in one extreme pivotal position of said mechanism and disengaged from said film mounting means in the other extreme pivotal position of said mechanism.

AMBROSIUS BRIECHLE. ROY T. HURLEY. GEORGE E. MERRI'I'I. 

